Modern ladders are of two general types, step ladders and extension ladders. Step ladders are ordinarily folding and have an A-shaped configuration, one side of which has a series of steps. Extension ladders, on the other hand, have two straight sections juxtaposed in parallel planes. These sections can be compressed for storage or transportation and subsequently extended to a desired length during use.
Because of the nature of the work for which step ladders and extension ladders are used, both types of ladders are often used upon surfaces which are uneven or irregular. Placing such ladders on irregular surfaces results in a substantial decrease in the stability of the ladder. The instability created increases with increasing ladder height.
To improve the stability of ladders under such conditions, workmen often place an object such as a rock or a wooden board under the bottom of one or more of the legs. While such spacers may level the ladder at a particular position, moving the ladder to another location may change the inclination of the base surface, requiring readjustment with different spacers. In addition to the time expended finding and positioning adequate spacers, movement of such unanchored spacers during use of the ladder can result in serious injuries. There is thus a great need to develop an apparatus to safely level ladders upon irregular surfaces.
A number of ladder leveling devices have been developed in an attempt to overcome the above problems. U.S. Pat. No. 4,029,174, for example, discloses a ladder designed for standing upon an incline or other uneven surface. The ladder is equipped with a metal block secured to a lower end of each leg. Each block has a threaded vertical opening in which a threaded extension is vertically adjustable. If the ground is sloped at an angle, one extension may be screwed into a lower position than the other so that both extensions rest firmly on the ground without the ladder being sidewardly inclined.
Similarly, U.S. Pat. No. 3,937,298, discloses an attachment for extension ladders which adjusts to uneven terrain. The attachment includes a pair of open-ended sockets mounted at opposite ends of a transverse member which is attached to the rails of an extension ladder. Two independently adjustable legs are slideably received, each in a receptive socket outward of the rails. A latching element associated with each socket locks one leg in a position of adjustment.
U.S. Pat. No. 4,683,983 also discloses a ladder leveling apparatus including a frame portion, a support portion, a slider portion, a retainer portion and a positioning portion. The frame portion includes an elongated U-shaped section having a main section of a width slightly larger than the width of a ladder leg. The slider portion includes a guide member disposed within a channel on the main section. The retainer portion is positioned over the guide member. A bolt extends through an opening in the retainer portion and a corresponding opening in the guide member. The bolt further extends beyond the main section a distance sufficient to pass through an opening across the thickness of the ladder leg and beyond. The positioning portion of the leveling device includes a traverse pin member that extends through aligned openings in the side sections of the frame portion.
Because of various shortcomings, however, no prior ladder leveling system has gained widespread acceptance. Some of these systems are very difficult to adjust for a number of reasons. These systems, for example, generally provide an adjustable leveling means only at the base of the ladder leg. Such designs require the user of the ladder to either adjust the leveling device while the ladder is on its side or to adjust the ladder while kneeling on the ground. Such inconvenience often causes the user to forego using the leveling system even if the ladder is equipped with such a system.
Other systems do not provide sufficient stability for safe use. Still others are too expensive to produce.
The present invention provides a novel safety ladder which overcomes the deficiencies of earlier devices. The present safety ladder provides a high degree of safety for the user, while being easily adjustable to quickly conform to almost any irregular surface.
Moreover, the present ladder is simple in design and can be produced relatively inexpensively. Current ladder manufacturing systems can easily be modified to manufacture the present ladder, and commercially available material and components can be used in the manufacture.